In image scanning apparatuses using electrophotographic methods, documents fed on platen glasses by, for example, automatic document feeders (ADFs) are scanned by charge coupled device (CCD) line sensors that extend in a direction (primary scanning direction) orthogonal to a conveying direction (secondary scanning direction) of the documents. In such image scanning apparatuses, if foreign objects, such as dusts (paper powder, etc.) or dirt, or scratches exist at scanning positions (specific positions in the conveying direction of the documents) on the platen glasses stripe patterns (hereinafter also referred to as black stripes) that extend in the conveying direction of the documents will appear on the scanned images. Some image forming apparatuses including such image scanning apparatuses detect such black stripes and notify users when black stripes are detected. For example, document scanning apparatuses are proposed, which display guidance (cleaning guidance) to prompt the users to do cleaning in order to remove the causes of black stripes if the black stripes are detected a certain number of times while normal scanning of documents of multiple pages is performed a certain number of times.
The black stripes that are caused by adherence of the foreign objects on the platen glasses can be cleared by the documents that are conveyed on the platen glasses to remove the foreign objects. However, the cleaning guidance may be displayed despite the fact that the foreign objects are practically removed and the apparatuses are returned to the normal state wherein no black stripe occurs when the cleaning guidance is immediately displayed upon detection of the black stripes on any of the pages that are automatically fed by the ADFs. In this case, unnecessary cleaning of the platen glasses is caused to be performed. As a result, a vicious cycle occurs in which the coating on the platen glasses is peeled off causing minor irregularities on the surfaces of the platen glasses and the foreign objects are more easily adhered on the platen glasses due to the irregularities.